PELVIS. 



175 



join three sacral ribs, corresponding, as we 

 have seen, to the three upper sacral vertebrae. 

 Mr. Carls le has seen them, in the negro, join 

 four sacral ribs, as above stated. 



The sacral element of the pelvis we have 

 found to be most largely developed in, Man, 

 and its angle with the spinal column most 

 marked, in adaptation to his destiny for the 

 erect and bipedal posture. In Birds, also, of 

 bipedal and semi- erect position of body, it is 

 also large, and, in a less degree, in animals 

 whose climbing or sedentary habits require 

 an habitual upright direction of the vertebral 

 column, such as the Apes, Bears, and Sloths ; 

 while it is much contracted, both in breadth 

 and length, in most of the animals of true 

 quadrupedal progression. Its spinous pro- 

 cesses arc long, and sometimes united in a 

 crest, in the springing animals, and those re- 

 quiring long leverage for the muscles of the 

 back and thigh arising therefrom. 



The coccygeal pieces are, in the human 

 subject and the higher Simue, the aborted 

 continuations of the sacral vertebrae, gradually 

 diminishing into their most permanent and 

 principal elements, the bodies of the ver- 

 tebrae. The upper ones show also rudimen- 

 tary transverse processes, and the first pre- 

 sents well marked articular processes to join 

 with those of the sacrum, or sacral horns. 

 Dr. Knox considers the 1st coccygeal ver- 

 tebra to be the representative, in man, of a 

 class of vertebra? distinct both from the sacral 

 and remaining coccygeal. 



In Man these bones are placed very obliquely, 

 to support the pelvic viscera ; but in the lower 

 mammals, the Birds, and especially the Reptiles 

 and Fishes, they are placed in the line of the 

 vertebral column, and are developed as caudal 

 vertebrae, in adaptation for their various uses in 

 propulsion or prehension, &c. In many, they 

 present not only a complete neural arch and 

 spine, enclosing the caudal continuation of 

 the spinal chord, but also an anterior or hcemal 

 arch and spine, to enclose .and protect the 

 arteries of the tail. 



The ilia evidently consist of the shafts of the 

 three or four sacral ribs, coalesced into one 

 mass of bone on each side, and constitute 

 the homologues of the shafts of the thoracic 

 ribs, termed by Owen the " pleitrapophyses." 

 The descending branch or body of the ischium 

 is considered by the same writer also to form 

 one of these plenrapophyses. The develop- 

 ment of the whole of the iscJihim, as well as 

 the pubis, from a single and separate centre ; 

 and the connection of both these bones to the 

 ilium in the cotyloid cavity, seems, however, to 

 place the whole of each bone in the same 

 relative position, and to class them both with 

 the chondro-sternal elements, or " hcemapo- 

 physcs *' of the thoracic ribs. Professor Owen 

 considers that the pubes and the ascend- 

 ing rarai only of the ischia are the homo- 

 logues of the rib cartilages, an arrangement 

 that would make a separation of the ischium, 

 which its mode of development from a single 

 centre would hardly justify. The bent and 

 hook-like form of the Mammalian ischia finds 



a very close counterpart in the cartilages of the 

 eighth ribs, in Man, especially when these 

 are ossified, as often occurs ; and the manner 

 of its junction with the pubes in the human 

 subject is exactly similar to that of the eighth 

 cartilage with the seventh, before it reached 

 the sternum. In many of the lower Mam- 

 malia, especially in the Marsupials and in the 

 Reptiles, we have seen that the ischial ribs 

 reach each other, and are connected, like 

 the pubic, in the median line. The formation 

 of a pubic apophysis or descending ramus to 

 meet the ascending ischium, is a disposition 

 which finds a counterpart in a similar apo- 

 physis from the acetabular end of the ischium 

 to support the pubes, which we have seen in 

 the pelvis of the Crocodiles, excluding the 

 latter bone from participating in the formation 

 of the acetabulum, exactly as the ischia in 

 man and some animals are excluded from the 

 formation of the median symphysis. The 

 greatest extent of this iscbio-pubic coales- 

 cence is seen in the Batrachians and the 

 saltatory Carnivora, Ruminants, and Marsu- 

 pials ; its entire absence in some of the Che- 

 Ionian and in the Saurian reptiles. In the 

 Birds and Bats it is often present even where 

 there is no median symphysis. 



The iliac element has been seen to be largely 

 developed in its shaft, and placed very ob- 

 liquely on the lumbar vertebras in quadrupeds 

 characterised chiefly by saltatory quadrupedal 

 progression, and requiring long hold for the 

 great muscles of the hip, as the Carnivora, the 

 Deer tribe, the Monkeys, the Horse, and the 

 Frog, while it is contracted to a remark- 

 able degree in the Walrus and Seal, which 

 approach in their habits the Cetaceans and 

 Fishes, in whom the iliac element of the pelvis 

 is the first to disappear altogether. Its alas 

 we see elongated behind the sacrum in those 

 animals whose pseudo-sedentary habits require 

 a long leverage for the muscles of the back 

 arising from the iliac crest, such as some of the 

 Rodcntia and the Kangaroos and its alas, on 

 the contrary, to be expanded in those requiring 

 support to the abdominal viscera, either from 

 their size, as in the Pachydermata, or from the 

 erect or semierect position, as in Man and the 

 Sloths. 



The ischiadic element has been seen to be 

 adapted by its large development and direct 

 line with the ilia, for saltatory progression, re- 

 quiring a long leverage for the flexor muscles 

 of the leg, as in the Carnivora, the Deer tribe, 

 the Rodents, the Kangaroos, and the Birds; 

 or, for the support of the sacrum, by its angu- 

 larity with the ilium, and by its elongated tube- 

 rosities, in the Ox, Hippopotamus, and some 

 others, and by ankylosis with the sacrum, as 

 in the Sloths, Bats, and Birds ; or for the 

 support of a carapace, as in the Armadilloes ; 

 or for the true ischial sedentary support of 

 the body, as in the Apes and Monkeys. 



The pubic element has been likewise seen to 

 be in a direct line with the iliac shaft in Man 

 only, destined to the truly erect posture; and 

 in those animals formed'for quadrupedal pro- 

 gression to be short and placed at a more or 



